Have you tried rebooting? All of your servers appear to be responding to basic TLS requests with the now expired R3 chain. I'm not sure why the full web requests would be timing out though. Do they connect to any back end servers over TLS as well that might be failing?
2008 R2 is way out of support at this point. So there hasn't been a lot of testing on how this expiry would affect it. But the reboot may force IIS to switch to the newer non-expired R3 chain.
If not, you may need to do some checking in the Windows cert stores to make sure the ISRG Root X1 cert is in the Trusted Roots store and possibly some additional tweaking in the Intermediate store.